Drive Trim: Finding the Sweet Spot

New to boating, or looking to optimize your time under way? It’s probably a good time to explain drive trim and what people mean when they talk about finding the “sweet spot.”

The sweet spot is the optimal trim setting for a given speed. It frees up the hull from the surface of the water and puts the engine under the lightest load, which is where you’ll get the best fuel economy at cruising speeds.

Better yet, I’ll teach you how to find it, rather than just tell you what it is. Here’s something you can try next time you’re out on the water. (The fewer boats around when you try this, the better.)

Drive trim is important for both speed and fuel economy. Some engine-control packages, like this one on a Boston Whaler, make the job easier.

While running at full throttle, trim the drive up until you see engine rpm spike but don’t feel any corresponding rise in speed. The whole boat will vibrate more than normal, and if you look behind you, you’ll see early signs of a James Bond-style rooster tail. That’s what too much trim feels like. It’s nothing to be afraid of, but it’s not the best way to travel. It’s also hard on the power train.

Now trim it down gradually, tapping the button down a little at a time till the vibration goes away, the prop grabs again, and the rooster tail subsides. The trim setting just before the vibration and other associated nonsense begins is where your boat will be fastest. You can either make a mental note of it, or mark your trim gauge with a piece of tape.

Try it a couple of times at different speeds. Sometimes the sweet spot at full throttle is different from the sweet spot at cruising speeds. It will also be affected by how the boat is loaded with people and gear, and the sea state.

Cruising in the sweet spot will improve your comfort and your fuel economy. But since there is really no such thing as true fuel economy in a powerboat, if you can get two mpg or better, call it good.